Device and method for manufacturing articles made of plastic

ABSTRACT

The invention is related to a device ( 1 ) and to a method for the injection molding of articles ( 25 ) with several plastic material components. This device ( 1 ) comprises a first half mold arranged as fixed ( 3 ), a second half-mold ( 6 ) arranged as movable relative to the first half-mold ( 3 ) for the purpose of opening and closing the device ( 1 ). In addition, the device ( 1 ) comprises at least two further half-molds ( 10, 11 ), which are arranged as jointly movable relative to the first and second half-molds ( 3, 6 ), and which in the closing position of the device ( 1 ) are situated between the first and the second half-molds ( 3, 6 ), so that in two parting planes ( 32, 33 ), namely in a first and in a second parting plane ( 32, 33 ), cavities ( 20, 21 ) are formed. The two further half-molds ( 10, 11 ) arranged as jointly movable comprise means ( 22 ), which in the case of an opened device ( 1 ) serve for the transportation of the article ( 25 ) out of a first cavity ( 21.1 ) into a second cavity ( 21.2 ) in such a manner, that the article ( 25 ) is capable of being injection molded around with a further material component in the second cavity ( 21.2 ).

[0001] The invention is related to a device and a method for manufacturing articles made of plastic material, e.g., brushes and in particular toothbrushes, in accordance with the generic terms of the independent claims.

[0002] Articles made of plastic material, in particular toothbrushes, are frequently manufactured out of differing materials and multicoloured. In the case of toothbrushes, for example, soft materials are combined with hard materials, wherein the soft materials, e.g., form gripping surfaces or flexing points. Toothbrushes of this type, which consist of several material components or which have several colours, are manufactured in special tools.

[0003] Known from prior art are various devices and methods for the manufacture of toothbrushes out of several material components. EP 0 0742 090, for example, demonstrates a device, which is based on a rotary table (star wheel tool). In this, individual material components are injected from one side into multi-part cavities, which in certain areas are actively connected with the rotary table situated in a single plane. The articles to be injection moulded around are moved by the rotary table from one cavity to the next lying in the plane, wherein they are held in a zone, which only comprises a single material component. All cavities have the same parting plane.

[0004] This device has the disadvantage, that, because of the cavities located adjacent to one another, it has to be built with very large dimensions, resp., that for this reason within a single cycle only a few articles can be manufactured. An integration of a device in accordance with this principle into a standard injection moulding machine, in the case of which the half-moulds are guided along spars, is uneconomical, because the distances between the spars of the injection moulding machine are standardised and as a result of this the maximum dimensions are limited.

[0005] It is the objective of the invention to demonstrate a device and a method, which makes possible an optimised manufacture of articles made of plastic material with several material components and colours.

[0006] The invention is explained in more detail on the basis of a toothbrush. For the specialist it is clear, however, that the invention is not restricted to the manufacture of articles of this type.

[0007] The objective is achieved by the invention defined in the claims.

[0008] Brush bodies of toothbrushes as a rule consist of a handle, which serves to grip the brush, a head, on which the bristles of the brush are affixed and a stem, which connects the handle with the head.

[0009] Toothbrushes as well as other articles made of plastic, which consist of several components or colours, today are manufactured by injection moulding. In doing so, the individual colours and material components are injected into cavities one after the other, in which in part intermediate products to be injection moulded around have been placed. The articles are moved from one cavity to the next by means of mechanical aids, in that they are held in a zone suitable for this, which only comprises a single material component. A brush body of a toothbrush, e.g., is preferably held in the zone of the head of the brush while it is moved from one cavity to the next, because this zone as a rule is not equipped with several materials. Through the choice of the materials and in particular of their melting points, it is guaranteed, that a component is not damaged while being injected around with a further component, resp., that it does not melt in an uncontrolled manner.

[0010] The half-moulds of an injection moulding mould for manufacturing injection moulded components are usually attached to mounting plates in an injection moulding machine. In this, a first half-mould is fastened to a fixed mounting plate and a second half-mould to a movable mounting plate, which in most instances is guided by four spars. Because in this the two half-moulds are arranged between the spars of the injection moulding machine, their maximum expanse is restricted by the distance between the spars. Today's moulds for the manufacture of articles made of plastic with several material components are based on star wheel tools with rotary tables, on which the part products are moved out of one cavity into another one. In doing so, the cavities are arranged adjacent to one another in a circle on a plane. In order to get from one cavity to the next one, the articles or the cavities are moved around the axis of the rotary table, which is arranged parallel to the spars of the injection moulding machine. This arrangement has the significant disadvantage, that the number of articles is massively limited because of the tight space conditions.

[0011] The invention divulged here demonstrates a device and a method, which significantly improves the manufacturing operation for articles made of plastic with several material—, resp., colour components. In contrast to methods known from prior art, the individual material—, resp., colour components are not manufactured in one plane on a rotary plate (star wheel tool), but manufactured in a tool with several levels (parting planes). This is a farther development of an injection moulding technology of the same applicant, which in part is already known from WO 99/28108.

[0012] The invention divulged here described in a simplified manner is based on the fact, that between a geographically fixed first and a movable second half-mould, each of which comprises at least one half-cavity, a third mould carrier is arranged as rotatable around an axis and displaceable at an angle to this axis, which serves to accommodate at least one third and one fourth half-mould with at least two half-cavities, which half-cavities of the third and fourth half-mould are actively connectable alternatingly with the first or second half-mould. These further half-moulds comprise means, in order to put in place articles (intermediate products) in the area of the further half-moulds from one half-cavity to the other, so that they can be injection moulded around with another material component in the other cavity on several sides. These means in preference are slides, which are at least partially integrated into a cavity.

[0013] The rotation axis of the third mould carrier in preference is arranged substantially vertically to the direction of movement of the movable second mould carrier and additionally translatorily displaceable in the same direction as the moveable second half-mould. The third and the fourth half-mould are affixed to two opposite sides of the third mould carrier and in the closed condition of the complete mould alternatingly act in conjunction with the first or with the second half-mould in two parting planes, so that on every side of the movable mould carrier at least one cavity is formed by the half-cavities of the half-moulds. By means of this injection moulding of material components in several planes it is achieved, that in contrast to the star wheel tools known from prior art more articles injection moulded around on several sides are capable of being manufactured with one tool. The closing forces necessary for sealing the mould, as a result of the several comparatively smaller separating planes, are correspondingly smaller.

[0014] The movements of the second half-mould as well as of the third and fourth half-moulds attached to the rotatable mould carrier in preference are coordinated with one another. The coordination can be designed as follows. When opening the mould the second half-mould is displaced translatorily relative to the first half-mould. Simultaneously, the mould carrier arranged to be movable with the third and the fourth half-mould, which in closed condition are arranged between the first and the second half-moulds, is moved translatorily with about half the speed of the second half-mould in the same direction as the second half-mould, so that the two separating planes are opened symmetrically. The movement is carried out to such an extent, that the movably arranged mould carrier with the third and the fourth half-moulds is capable of being rotated around its axis, so that the articles from a first material component are capable of being moved out of one cavity in the area of the first parting plane, on the side of the fixed first half-mould, into a cavity in the area of the second parting plane on the side of the movable second half-mould.

[0015] In the case of brush bodies, for example, which around their handles (e.g., at the top and at the bottom) comprise several material components or colours, it is necessary, that the cavities have different shapes for the differing material components. For this reason, a change of cavity is necessary for the second material component. The articles for this purpose are held gripped in a zone, into which no second component is injection moulded on and in this manner out of the first cavity are placed into a second one. Toothbrushes in preference are held gripped in the zone of the brush head at the apertures for the bristles. The holder for transferring the articles from one cavity into a further one in preference is integrated into the half-moulds, which are moved along with the third mould carrier, resp., which forms a part of the cavities themselves.

[0016] The movably arranged middle mould carrier if so required can comprise more than two opposite areas, which are suitable for receiving half-moulds. As a result, it is possible, e.g., that articles during the displacement from a first to a second injection moulding position are subjected to a cooling phase, finished parts removed or further components injection moulded.

[0017] The movable mould carrier is in preference guided by at least one cross-head, which is, e.g., displaceably mounted on the spars of the injection moulding machine. Particularly advantageous is an arrangement with two cross-heads, which guide the mould carrier on two sides and which are capable of being moved independently of one another, so that the mould carrier and the half-moulds assigned to it can be installed and removed in a particularly simple manner.

[0018] The rotary bearing of the rotatable mould carrier is designed in such a manner, that the media and information, such as cooling liquids, hydraulic oil, electric power and data are coaxially transferred, resp., exchanged in the zone of the rotary bearing. The bearings in preference are designed in such a manner, that no limitation in any direction of rotation is present.

[0019] The mould, resp., the half-moulds and/or the mould carriers in preference comprise means for measuring the condition of the process and/or means for storing in memory the condition of the process. These means can be utilised for the purpose of, for example, adjusting the optimum parameters in the case of a tool change. The half-moulds in preference are connected with the injection moulding machines through standard interfaces, so that a maximum interchangeability is guaranteed. By means of a standardisation of interfaces for the transfer of media, such as cooling liquids (water, gas, oil), hydraulic—, electrical—and mechanical energy as well as also information and signals, it is possible to match moulds and injection moulding machines with one another in such a manner, that a change in the course of a manufacturing process is capable of being carried out in a very short time. The interfaces are defined in such a manner, that they are capable of being suitably combined for several moulds.

[0020] The devices for the injection moulding of articles made of plastic divulged here in preference comprise means for the storage in memory of information. These are, e.g., microprocessors, data storage units, etc. They are advantageously integrated into a half-mould and they contain relevant data concerning the mould, a manufacturing process, the materials utilised, etc. These means for the storage in memory are connected with the injection moulding machine through defined interfaces and if so required also with further devices. The interfaces are conceived in such a manner, that they are able to be utilised in a variety of ways. It is therefore possible, e.g., to design several moulds for an existing machine with a defined interface.

[0021] The moulds comprise accordingly corresponding interfaces. The moulds comprise means for the storage in memory of information. In these, during the manufacturing process all relevant data are stored in memory. These are either determined in advance by calculation or by means of tests or else are established during the production process. In doing so, these data are not fixed, but rather changeable as and when required in such a manner, that, e.g., certain values obtained from experience are capable of being taken into consideration. If during the production a change of the manufacturing process is necessary, then the relevant data are updated when required, active interfaces are released from the mould and the injection moulding machine, the mould is removed from the injection moulding machine and replaced by another one, which also comprises a corresponding interface, which can be actively connected. The interfaces for the transferring of media advantageously comprise self-sealing couplings. These are constructed in such a manner, that the interfaces can be connected and disconnected without any significant loss of media. When inserting a mould into an injection moulding machine, the interfaces of the mould and of the machine are actively connected. From the means for the storage in memory of data, e.g., all relevant data are transferred to the injection moulding machine in such a manner, that it optimally adapts itself to the mould. In doing so, e.g., volume flows of the cooling medium, the temperature of the heating elements, the closing pressure of the machine, cycle times, injection parameters, etc., are transferred. The means for the storage in memory of data if so required or also alternatively may consist of a microprocessor, which, e.g. monitors the values of sensors or operates the regulated values. The relevant data advantageously are transmitted as digital signals. A corresponding device can also be utilised for safeguarding the production process, inasmuch as, for example, safety functions are monitored and executed. It is possible, e.g., to monitor service values, which define when a mould has to be serviced (for example, the number of cycles, etc.). In a machine it is possible to utilise more than one interface.

[0022] For example, for assembly injection moulding, both the fixed first—as well as the movable second half-mould can comprise means for a change of cavities. As a result it is possible to introduce additional material components.

[0023] The method divulged here for the injection moulding of an article made up of several plastic components can in a simplified manner be described as follows. In a first step, in a working position of the injection moulding machine a first liquid plastic material is injected into a cavity in the zone of a first parting plane of the injection moulding machine for the purpose of moulding an article. In a second step, the article made out of the first plastic material after solidifying or in a partially plastic condition after opening the injection moulding device is brought from the first cavity in the zone of the first parting plane into a second cavity in the zone of a second parting plane, which is located at a distance from the first parting plane, where in a third step in the working position of the injection moulding machine it is injection moulded around with a further plastic material component. It is advantageous, that while in the second cavity the article is being injection moulded around with the further plastic material component, simultaneously in the first cavity a further article is being injection moulded.

[0024] The invention is explained in more detail on the basis of the following Figures. These schematically and in a strongly simplified manner illustrate:

[0025]FIG. 1 a device for the manufacture of toothbrushes,

[0026]FIG. 2 the device in accordance with FIG. 1 in a further representation,

[0027]FIG. 3 an excerpt from FIG. 2.

[0028]FIG. 1 schematically and in a strongly simplified manner and in a perspective view illustrates a preferred embodiment of an injection moulding mould 1 according to the invention for the manufacture of toothbrushes. A first, fixed mould carrier 2 serves as the base for a first, fixed half-mould 3. Four spars 4 connected with this first mould carrier 2 serve for bearing a second mould carrier 5, which is arranged as displaceable along the spars 4. The mould carrier 5 serves as base for a second half-mould 6, which is arranged as displaceable.

[0029] Visible between the first and the second mould carriers 2, 5 is a third mould carrier 7, which here is supported between two cross-heads 8 and is rotatable around an axis A and arranged to be displaceable with the cross-heads and which serves as a base for a third and fourth half-moulds 10, 11. The axis A is substantially vertical to the spars 4. The cross-heads 8 are arranged to be displaceable along the spars 4 independently of one another, so that the third one of the mould carriers 7 is particularly easily removable and installable from above between the spars. The cross-heads 8 are displaceable along the spars 4 by means of actuating means, here in the form of hydraulic cylinders 9.

[0030] The device 1 is illustrated in an opened position, so that the cavities 20 of the movable, second half-mould 6 and the cavities 21 of the third half-mould 10 are visible. The third and the fourth half-moulds 10, 11 comprise slides 22, which serve for moving articles made of a first material component out of a first cavity into a further one (in this context, refer to the description for FIG. 3), so that the articles can be injection moulded around on several sides. The movement of the slides is designed in such a manner, that the articles are moved out of the first cavity, displaced and placed inside a second cavity, so that they can be injection moulded around with a further material component.

[0031] The injection moulding mould 1 is utilised in conjunction with an injection moulding machine (not illustrated here in detail). The injection moulding machine comprises means for pressing the half-moulds 3, 6, 10, 11 against one another during the injection moulding process, so that hollow spaces are formed by the cavities 20, 21. The spars 4 may be spars of the injection moulding machine or else separate guiding means.

[0032] The molten plastic mass is injected into the cavities 20, 21 formed by the half-moulds 3, 6, 10, 11 through apertures 30, 31 situated opposite the half-moulds in the mould carriers 2, 5 in the closed condition (working position) of the injection moulding mould 1. The apertures 30, 31 verge into channels with branch-offs, which extend through the first and the second mould carrier 2, 5 right into the cavities 20, 21. The device for introducing the molten plastic mass through the apertures 30, 31 in the second mould carrier 5 is arranged to be movable, so that the device 1 is capable of being opened and closed. As can be identified, in contrast to the devices known from prior art, articles of differing shape are simultaneously injection moulded in several parting planes 32, 33, which are located at a distance from one another.

[0033]FIG. 2 schematically and in a strongly simplified manner depicts a “snap-shot” of the injection moulding mould in accordance with FIG. 1 while the third mould carrier 7 and with it the third and fourth half-moulds 10, 11 with the injection moulding mould 1 opened are rotated in the direction of an arrow 23 by 180° around the axis A. As can be identified, the third half-mould 10 (and in an analogous manner the fourth half-mould 11) comprise slides 22, which serve for the displacement of articles 25 out of one cavity into another cavity 21.1, 21.2 (refer to FIG. 3), while the third and the fourth half-moulds 10, 11 are moved around the axis A. In the further cavity 21.1, the articles after the closing of the injection moulding mould 1 are injection moulded around with a further material component.

[0034] The half-moulds 3, 6, 10, 11 each comprise four rows of cavities 20, 21, wherein the cavities 21.1, 21.2 of the third and of the fourth half-moulds 10, 11 are each implemented as double. This is necessary, in order to be in a position to injection mould around the articles 25 with a further material component by displacement from two sides.

[0035]FIG. 3 illustrates an excerpt D from FIG. 2. In this Figure, by means of arrows 34.1, 34.2, 34.3 it is schematically illustrated, how the articles 25 by means of the slide 22 are transferred out of a first to a second half-cavity 21.1, 21.2. The articles 25 are brush bodies of toothbrushes. The brush bodies 25 are held gripped in the zone of their head 26 by the slide 22, while their handles 27 are transferred to a further cavity. 

1. Device (1) for the injection moulding of articles (25) comprising several plastic material components, with a first half-mould (3) arranged as fixed, with a second half-mould (6) for the purpose of opening and closing the device (1) arranged as movable relative to the first half-mould (3), and at least two further half-moulds (10, 11) arranged to be jointly movable relative to the first and the second half-moulds (3, 6), the further half-moulds (10, 11) in closing position of the device (1) being arranged between the first and the second half-moulds (3, 6) in such a manner, that in two parting planes (32, 33), namely in a first and in a second parting plane (32, 33), cavities (20, 21) are formed, characterised in that the two further half-moulds (10, 11) arranged to be jointly movable comprise means (22), which with the device (1) opened serve to transport an article (25) out of a first cavity (21.1) into a second cavity (21.2) in such a manner, that the article (25) is capable of being injection moulded around with a further material component in the second cavity (21.2).
 2. Device (1) in accordance with claim 1, characterised in that the means (22) is a slide (22).
 3. Device (1) according to one of the preceding claims, characterised in that the means (22) is integrated into a cavity (20, 21).
 4. Device (1) in accordance with one of the preceding claims, characterised in that a mould carrier (7) is present, which is supported on a bearing capable of being around an axis (A) and arranged to be displaceable at an angle relative to this axis, and which serves to receive and to jointly move the two further half-moulds (10, 11) in such a manner, that the two further half-moulds (10, 11) with the device (1) opened by rotation of the mould carrier (7) around the axis (A) for the purpose of forming cavities (20, 21) are capable of being brought into the working position alternatingly with the first or with the second half-moulds (3, 6).
 5. Device (1) according to claim 4, characterised in that the mould carrier (7) is displaceable by 180° around the axis (A) at a right angle to it.
 6. Device (1) in accordance with claim 5, characterised in that the mould carrier (7) is respectively supported on two sides by a cross-head (8) in the manner of a bearing, in such a way, that the mould carrier (7) with the device (1) opened is capable of being rotated around the axis (A) and jointly movable with the cross-heads (8).
 7. Device (1) according to claim 6, characterised in that the cross-heads (8) are guided on spars (4).
 8. Device (1) in accordance with claim 7, characterised in that the cross-heads (8) for the purpose of installing and removing the mould carrier (7) and/or the further half-moulds (10, 11) are displaceable independently of one another.
 9. Device (1) according to one of the claims 7 or 8, characterised in that the spars (4) serve for guiding the second, movable half-mould (6).
 10. Method for the injection moulding of an article made of several plastic material components, in the case of which in a first step in a working position of a device (1) a first liquid plastic material is injected into a first cavity (20, 21.1) in the zone of a first parting plane (32) of the device (1) for the moulding of an article (25), in a second step the article (25) made of the first plastic material with the device (1) opened in the zone of the first parting plane (32) is brought out of the first cavity (20, 21.1) into a second cavity (20, 21.2) in the zone of a second parting plane (33) situated at a distance relative to the first parting plane (32), where in a third step it is injection moulded around with a further plastic material component in the working position of the device (1).
 11. Method according to claim 10, characterised in that, while in the second cavity (20, 21.2) the article (25) is being injected around with the further plastic material component, simultaneously in the first cavity (20, 21.1) a further article (25) is being injection moulded.
 12. Method in accordance with one of the claims 10 or 11, characterised in that the article (25) during the transfer into the second cavity (20, 21.1) is rotated around an axis (A) and laterally displaced (34.1, 34.2, 34.3).
 13. Method according to one of the claims 10 to 12, characterised in that the first cavity (20, 21.1) is formed by a first half-mould (3) and alternatingly by one of at least two further half-moulds (10, 11), which are jointly arranged to be capable of being rotated relative to the first half-mould (3) around an axis (A) and displaceable in parallel to it and that the second cavity (20, 21.2) is formed by a further half-mould (6) opposite the first and the two half-moulds (10, 11), which are jointly capable of being rotated around an axis and is alternatingly formed by one of these two half-moulds. 